BITS_PER_ITER
#ifndef BITS_PER_ITER
#if BITS_PER_ITER == 32
reps = 64 / BITS_PER_ITER;
reps -= 32 / BITS_PER_ITER;
#if BITS_PER_ITER == 16
d_msig = (d >> (64 - BITS_PER_ITER)) + 1;
q_digit = (unsigned long)(~n_hi >> (64 - 2 * BITS_PER_ITER)) / d_msig;
overflow = n_hi >> (64 - BITS_PER_ITER);
n_hi = add_u64_u32(n_hi << BITS_PER_ITER, n_lo >> (64 - BITS_PER_ITER));
n_lo <<= BITS_PER_ITER;
while (overflow < 0xffffffff >> (32 - BITS_PER_ITER)) {
quotient = add_u64_long(quotient << BITS_PER_ITER, q_digit);